Resolution Guide

Digital images are made up of small squares of color called pixels. The more pixels in an image file, the higher the resolution. This determines the level of detail in the image, affecting sharpness, color richness, and overall quality.

Excellent quality photo prints require a resolution of at least 300 dpi (dots per inch).

Therefore, an image file should ideally measure at least 1200 pixels by 1800 pixels to print an excellent quality 4x6 print. This is because 4 inches x 300 dpi = 1200 pixels and 6 inches x 300 dpi = 1800 pixels.

A megapixel (abbreviated MP) is a million pixels, usually referring to the image sensor of a digital camera. Most current models of digital cameras and smart phones feature sensors anywhere from 8 to 40 megapixels.

Consult the follow table for a guide to camera resolutions (in MP) and their corresponding print quality in various common sizes:
A = Excellent quality
B = Good quality
C = Fair quality
X = Poor (Not recommended)
Inches: 8
12 16 18 24 36 40
5x7 A A A A A A A
8x10/8x12 A A A A A A A
11x14/12x18 B A A A A A A
16x20/16x24 C B B B A A A
20x30 X C B B B A A
24x36 X X C C B B A
30x40 X X C C C B B
40x60 & Up

Image resolution (number of pixels) does not correspond exactly to file size, which is measured in kilobytes or megabytes. But generally speaking, larger file sizes are higher resolution and better for printing.

You can often get away with upscaling the file if it's relatively close in size. However, it is sometimes difficult to determine if an image is too small to print with good or excellent quality based on file size or pixel dimensions alone. To some degree, terms like "good" and "excellent" are subjective. You can always consider viewing a proof print when in doubt.

In many cases, photo editing software, email software, and smart phone and tablet apps will downsize photo files by default, making them too small to print. This can be avoided by changing the settings or not using the software for printable files.

Jpeg files are preferred for photo printing. While it is true that jpeg files compress the image data for a smaller file size, the image is still displayed and printed at full resolution. Jpeg files are lossy, however they only lose quality when edited/saved over and over excessively.

Click here to learn more about image resolution.